Electronic percusion – part.2 (snare drum)

Here’s what the snare looks like at the moment. Nothing magical, in fact, It’s one from the traditional twin T oscillator found in many old drum machines. The first idea was to use only transistors. However, after few experimentations with the modular, the added noise is quite a key element of the expected snare drum sound. So I added that part (obviously, the white noise will be taken from the noise of the previous circuit)

.snare_percu_jpeg

I didn’t want to go building another differential amp VCA or use another OTA, and so far I was quite away from the “transistor only” idea. I wanted to keep it simple, so the circuit is using a vactrol based VCA to control the noise added to the snare. It isn’t cheap but I think any kind of led/lrd would do the job, no specific need for an expensive VTL something. Speed isn’t a concern unless you want a snare hiting at 15hz…

R5 is the gain trimmer and its setting will depend on the transistor’s gain. Be careful, this circuit can go into oscillation if there’s too much gain (it is an oscillator after all). R11 is the “tune” control for the oscillator. R34 can be changed for a fixed resistor, it basically sets the decay of the added noise. You want it to be short but I guess one can also consider a pot in front for it.

Nonetheless, if I was less lazy I’d make a total transistor path for the sound (there’s no real interest to make the trigger circuit transistor based). Maybe I’ll do it…

Obviously, some adjustements have to be made, the noise should be lower in volume than the oscillator into the final mixer. But those will be made at the “soldering” stage, There’re things that you can’t know until you build the thing.

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3 Comments

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3 responses to “Electronic percusion – part.2 (snare drum)

  1. Gordon

    I done a lot of experimenting with analog electronic percussion circuits about 13 years ago. By far the best results I had creating a snare sound was with digitally generated noise using the 4006 chips, like in the TR909. digital noise with or without filtering works well and has the unusual ability to “tune” the noise by making the clock oscillator that drives the 4006 variable. With the clock turned way down low you could get a nasty lofi crunchy sort of sound a bit like 8 bit computer sound fx!

    • hi,
      thanks for the trick. Isn’t the CD4006 obsolete ?

      I’ve just looked at the datasheet and some application. Looks like a linear feedback shift register actually.

      You just gave me an idea for a project of mine which needs more stuff.

      • Gordon

        They are, more or less but see later. I have a stash of them that I am very reluctant to part with. I sold 2 ssm2045’s a couple of years ago and regret it now. As for the 4006 their are a couple of options; You could use other shift register chips, the 4015 is still in production by TI. The other option is that for some strange reason TI still manufactures the 4006 in the Mil-Spec variety, they are $16.00 each in quantities of 100!!!!! Must be some funky cold war missile circuits that still use them!

        As for using the 4015’s, you will need several as they are only dual 4 bit shift register, therefore a maximum of 8 stages per chip. In comparison the 4006 was an 18 stage shift register. If you do a Google search for 4015 based noise generator you can find some interesting stuff. I will try to get a schematic of my noise circuit and perhaps an equivalent realization of it using 4015’s in a n internet shareable format, as all that work was done with pen and paper!

        Gordon.

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